In the field of ball-hitting implements, and particularly tennis rackets, it has long been the practice to lighten the racket body to make the racket easier to swing, and to adjust the balance (distribute the weight) to shift the center of gravity of the racket.
There have also been proposals aimed at reducing discomfort such as numbness or excessive load on the body by suppressing or absorbing (attenuating) the impact vibration at the instant the ball is hit.
For instance, Japanese Patent 2,853,926 and Japanese Patent Application Laid-Open No. H4-263876 disclose the provision of this sort of means to a grip end.
In these prior art, it is proposed that a loading member (weighting body) be mounted as a vibrator via an impact vibration-absorbing member. The effect of this proposal is said to be that it eliminates the increase in impact that occurs when a conventional weight is directly mounted to a grip end.
With the above prior art, however, the impact vibration-absorbing member and the loading member are either housed within the grip or attached on the outside; and there is no mention of the importance of balancing (weight distribution), especially as regards the weight pertaining to the weighting structure of the present invention (an increase in the moment of inertia around the center of gravity), nor is there any mention that the feel of hitting the ball is improved when the non-impact position (node of vibration) of the two-node flexural vibration on the grip produced when the racket hits the ball is shifted to the portion grasped by the hands (grip fulcrum).
Meanwhile, an overview of the main balancing means (including stabilizers) used to absorb impact vibration reveals that some are provided to the racket head (frame) or the middle part (throat), rather than to the grip end, but there is no mention whatsoever of the structure of the present invention, so a proposal such as this is outside the body of prior art.
In light of this, the inventor has already proposed a “Balancing Weighting Body for Ball-Hitting Implement” (Japanese Patent Application No. 2000-65171). In this application, the balancing means required to solve the above problem, and more specifically, a balancing weight protruding from the grip end bottom of a ball-hitting implement, is provided. The center of gravity position is shifted toward the portion grasped by the hands, and the moment of inertia around the center of gravity is increased, which raises head speed by facilitating snap movement centered around the wrist, and also absorbs impact vibration, thereby improving the characteristics of the ball-hitting implement.
The characteristic feature proposed here is to provide a balancing weight protruding from the bottom of the grip end cap or end rubber of the ball-hitting implement; and while the general object and effect were the same as in the present invention, there is room for improvement in the weight and the attendant weighting structure, including the distribution of weight for moving the center of impact (node of vibration) on the grip.
The general trend in tennis rackets in recent years has been to make them lightweight and top-heavy, This means that the node of vibration on the grip is farther away from the grip end when the ball is hit. While this does improve rebound, it also increases impact (vibration). The node of vibration is usually 90 to 180 mm (3.6 to 7.2 inches) away from the grip end, although this varies with differences in weight distribution.
The present invention is conceived in light of this situation; and it provides a grip end bottom weight and a grip end bottom weighting structure which raise the level of play, and afford simple mounting on the grip end bottom, which makes a racket easier to handle, which in turn increases head speed, and improves the damping effect (especially moving the node of vibration on the grip) in order to prevent injury and make it more comfortable to hit the ball.
As to applications of the present invention, a tennis racket is typical; however, the present invention is not limited to this and can be applied to soft tennis rackets, squash rackets, badminton rackets, or other such rackets, or to baseball or softball bats, golf clubs, ground golf clubs, gate ball clubs, hockey sticks, and other such ball-hitting implements.